banan-os/userspace/aoc2023/day13/main.cpp

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2023-12-19 01:25:23 +02:00
#include <BAN/Optional.h>
#include <BAN/String.h>
#include <BAN/Vector.h>
#include <ctype.h>
#include <inttypes.h>
#include <stdio.h>
using i8 = int8_t;
using i16 = int16_t;
using i32 = int32_t;
using i64 = int64_t;
using u8 = uint8_t;
using u16 = uint16_t;
using u32 = uint32_t;
using u64 = uint64_t;
using Grid = BAN::Vector<BAN::String>;
BAN::Optional<i64> calculate_score(const Grid& grid, i64 skip_val = 0)
{
// horizontal reflection
for (size_t x = 1; x < grid.front().size(); x++)
{
const size_t reflection_len = BAN::Math::min(x, grid.front().size() - x);
bool has_reflection = true;
for (size_t y = 0; y < grid.size() && has_reflection; y++)
for (size_t x_off = 0; x_off < reflection_len && has_reflection; x_off++)
if (grid[y][x - x_off - 1] != grid[y][x + x_off])
has_reflection = false;
if (has_reflection && (i64)x != skip_val)
return x;
}
// vertical reflection
for (size_t y = 1; y < grid.size(); y++)
{
const size_t reflection_len = BAN::Math::min(y, grid.size() - y);
bool has_reflection = true;
for (size_t x = 0; x < grid.front().size() && has_reflection; x++)
for (size_t y_off = 0; y_off < reflection_len && has_reflection; y_off++)
if (grid[y - y_off - 1][x] != grid[y + y_off][x])
has_reflection = false;
if (has_reflection && (i64)y * 100 != skip_val)
return y * 100;
}
return {};
}
i64 puzzle1(FILE* fp)
{
i64 result = 0;
char buffer[128];
while (fgets(buffer, sizeof(buffer), fp))
{
Grid grid;
while (buffer[0] != '\n')
{
ASSERT(buffer[strlen(buffer) - 1] == '\n');
buffer[strlen(buffer) - 1] = '\0';
MUST(grid.emplace_back(buffer));
if (fgets(buffer, sizeof(buffer), fp) == nullptr)
break;
}
result += *calculate_score(grid);
}
return result;
}
i64 puzzle2(FILE* fp)
{
i64 result = 0;
char buffer[128];
while (fgets(buffer, sizeof(buffer), fp))
{
Grid grid;
while (buffer[0] != '\n')
{
ASSERT(buffer[strlen(buffer) - 1] == '\n');
buffer[strlen(buffer) - 1] = '\0';
MUST(grid.emplace_back(buffer));
if (fgets(buffer, sizeof(buffer), fp) == nullptr)
break;
}
i64 original = *calculate_score(grid);
for (size_t y = 0; y < grid.size(); y++)
{
for (size_t x = 0; x < grid.front().size(); x++)
{
grid[y][x] = (grid[y][x] == '.') ? '#' : '.';
if (auto res = calculate_score(grid, original); res.has_value())
{
result += *res;
goto grid_done;
}
grid[y][x] = (grid[y][x] == '.') ? '#' : '.';
}
}
ASSERT_NOT_REACHED();
grid_done:
continue;
}
return result;
}
int main(int argc, char** argv)
{
const char* file_path = "/usr/share/aoc2023/day13_input.txt";
if (argc >= 2)
file_path = argv[1];
FILE* fp = fopen(file_path, "r");
if (fp == nullptr)
{
perror("fopen");
return 1;
}
printf("puzzle1: %" PRId64 "\n", puzzle1(fp));
fseek(fp, 0, SEEK_SET);
printf("puzzle2: %" PRId64 "\n", puzzle2(fp));
fclose(fp);
}